An experimental investigation of the effects of chronic stress on bone-to-implant contact

OBJECTIVES: This study aimed to investigate the effects of chronic restraint stress on the osseointegration of titanium implants. MATERIALS AND METHODS: Twenty adult male Wistar albino rats were used in the study. After surgical insertion of titanium implants into the metaphyseal part of the tibial bone, rats were randomly divided into two groups: a control group (CNT group) and an experimental restraint stress group (RS group). In the CNT group, titanium implants were inserted surgically, and rats received no further treatment during the 47-day experimental period. In the RS group, restraint stress was applied for 3 hours per day for 45 days, beginning 2 days after implant surgery. Weight of the rats was measured prior to surgery and at the end of the study to analyze the effects of stress. At the end of the experimental period, rats were euthanized, and implants and surrounding bone tissues were used for undecalcified histological analysis. Serum cortisol levels were assessed in cardiac blood samples from the rats following centrifugation. RESULTS: Average weight of rats in the RS group was lower than that of rats in the CNT group after the experimental protocol had been completed (P0.05). CONCLUSION: The data analyzed in this study suggest that chronic restraint stress did not adversely affect rats during a 45-day osseointegration period.

The effect of undersizing and tapping on bone to implant contact and implant primary stability: A histomorphometric study on bovine ribs

PURPOSE: Implant site preparation may be adjusted to achieve the maximum possible primary stability. The aim of this investigation was to study the relation among bone-to-implant contact at insertion, bone density, and implant primary stability intra-operatively measured by a torque-measuring implant motor, when implant sites were undersized or tapped. MATERIALS AND METHODS: Undersized (n=14), standard (n=13), and tapped (n=13) implant sites were prepared on 9 segments of bovine ribs. After measuring bone density using the implant motor, 40 implants were placed, and their primary stability assessed by measuring the integral of the torque-depth insertion curve. Bovine ribs were then processed histologically, the bone-to-implant contact measured and statistically correlated to bone density and the integral. RESULTS: Bone-to-implant contact and the integral of the torque-depth curve were significantly greater for undersized sites than tapped sites. Moreover, a correlation between bone to implant contact, the integral and bone density was found under all preparation conditions. The slope of the bone-to-implant/density and integral/density lines was significantly greater for undersized sites, while those corresponding to standard prepared and tapped sites did not differ significantly. CONCLUSION: The integral of the torque-depth curve provided reliable information about bone-to-implant contact and primary implant stability even in tapped or undersized sites. The linear relations found among the parameters suggests a connection between extent and modality of undersizing and the corresponding increase of the integral and, consequently, of primary stability. These results might help the physician determine the extent of undersizing needed to achieve the proper implant primary stability, according to the planned loading protocol.

Osseointegration of Magnesium-Incorporated Sand-Blasted Acid-Etched Implant in the Dog Mandible: Resonance Frequency Measurements and Histomorphometric Analysis

The aim of this pilot study was to investigate the bone responses of novel magnesium (Mg)–incorporated sand-blasted and acid-etched (SLA) titanium (Ti) implant in an experimental animal model. Novel Mg-incorporated SLA Ti implant was obtained via vacuum arc source ion implantation method and Mg-ions were implanted into the SLA implant surface. Control group consisted of two commercial implants; resorbable blasting media (RBM) and SLA. Twelve implants from each group were placed into the mandibles of 6 mongrel dogs. Experimental animals were divided into 2 groups of 3 animals, with 4 weeks and 8 weeks healing time points. Resonance frequency analysis was performed at the time of fixture installation, 1, 2, 4, and 8 weeks after installation. Bone to implant contact (BIC) measurements were assessed at the 4 and 8 weeks healing time points. The overall implant survival rate was 97.2%. The Mg-incorporated SLA Ti implants showed more rapid osseointegration than control group implants at follow-up periods of 4 weeks. Histomorphometric analysis showed a tendency for BIC% values of Mg-incorporated SLA Ti implant to be higher than that of other the implant groups. The results of this study suggest that Mg-incorporated SLA Ti implant may be effective in enhancing the bone responses by rapid osseointegration in early healing periods.

On the osseointegration of zirconia and titanium implants installed at defect site filled with xenograft material / 대한치과보철학회지

PURPOSE: The purpose of this study was to compare zirconia implants with titanium implants from the view point of biomechanical stability and histologic response on osseointegration when those were placed with xenograft materials. MATERIALS AND METHODS: Specimens were divided into two groups; the control group was experimented with eighteen titanium implants which had anodized surface and the experimental group was experimented with eighteen sandblasted zirconia (Y-TZP) implants. At the tibias of six pigs, implants were installed into bone defect sites prepared surgically and treated with resorbable membranes and bovine bone. Two pigs were sacrificed after 1, 4 and 12 weeks respectively. Each implant site was sampled and processed for histologic and histomorphometric analysis. The stability of implants was evaluated with a Periotes(R). And the interfaces between bone and the implant were observed with a scanning electron microscope. RESULTS: In stability analysis there was no significant difference between Periotest values of the control group and the experimental group. In histologic analysis with a light microscope after 4 weeks, there was new bone formation with the resorption of bovine bone and the active synthesis of osteoblasts in both groups. In bone-implant contact percentage there was significant difference between both groups (P<.05). In bone area percentage there was no significant difference between both groups. In analysis of both groups with a scanning electron microscope there was a gap between bone and a surface at 4 weeks and it was filled up with bone formed newly at 12 weeks. CONCLUSION: When accompanied by xenograft using membrane, bone to implant contact percentage of zirconia implants used in this experiment was significantly less than that of the titanium implants by surface treatment of anodic oxidation. So, it is considered that the improvement of zirconia implant is needed through ongoing research on surface treatment methods for its practical use.

Osseointegration of zirconia implant in the tibia of pigs / 대한치과보철학회지

PURPOSE: The purposes of this study were to investigate osseointegration around zirconia implants which had machined or alumina sandblasted surface, and to compare the results with titanium implants. MATERIALS AND METHODS: The study was performed on the tibia of 6 pigs. Three types of implants were investigated: group T-titanium implant, group Z-machined zirconia implant, group ZS-alumina sandblasting treated zirconia implant. Zirconia implants were manufactured from yttria-stabilized tetragonal zirconia polycrystalline (Acucera Inc., Pocheon, Korea). A total of 36 implants were installed in pigs' tibias. After 1, 4 and 12 weeks of healing period, the periotest and the histomorphometric analysis were performed. The data were analyzed using one-way ANOVA and significance was assessed by the Scheffe test (alpha=.05). RESULTS: In the measurement of surface roughness, highest Ra value was measured in group T with significant difference. No significant differences were found among groups regarding Periotest values. After 1 week, in comparison of bone to implant contact (BIC), group Z showed higher value with significant difference. In comparison of bone area (BA), group T and group Z showed higher value with significant difference than group ZS. After 4 weeks, in comparison of BIC, group T showed higher value with significant difference. Comparison of BA showed no significant difference among each implant. After 12 weeks, the highest mean BIC values were found in group T with significant difference. Group ZS showed higher BIC value with significant difference than group Z. In comparison of BA, group T and group ZS showed higher value with significant difference than group Z. CONCLUSION: Zirconia implant showed low levels of osseointegration in this experiment. Modification of surface structure should be taken into consideration in designing zirconia implants to improve the success rate.

The effect of PostGraft(TM) on implants were installed at the tibia of ovariectomized rats / 대한치과보철학회지

PURPOSE: This study evaluated PostGraft(TM) which enhances implant stability and bone density. MATERIALS AND METHODS: Forty eight implants were installed at the tibia of ovariectomized rats. The group administrated with PostGraft(TM) was the experimental group, and the control group was not administrated. Implant stability was evaluated at the 2nd, 4th and 6th week by Periotest value, bone mineral density, bone-to-implant contact. These values were analyzed statistically with Mann-Whitney U test (P<.05). Histological analysis was evaluated at the 2nd, 4th and 6th week. RESULTS: According to the Periotest(R) measurement, both experimental and control groups showed decrease in values as time elapsed. Greater decrease was observed in the experimental group but there was no significant difference. By examining the radiographic images, both experimental and control groups showed tendency of increase in bone density. Greater increase was seen in the experimental group but there was no significant difference. According to the bone-to-implant contact measurement, both experimental and control groups showed increase in values as time elapsed. Greater increase was seen in the experimental group. At the 2nd and 4th week, there was no significant difference. But at the 6th week, there was significant difference (P<.05). By histological analysis, both experimental and control groups showed increase in bone formation as time elapsed. In addition, greater increase was seen in the experimental group. CONCLUSION: It could be concluded that the PostGraft(TM) medicated group showed better results in the bone density and osseointegration.

A histomorphometric study of dental implants with different surface characteristics

PURPOSE: One of the major keys to achieve successful osseointegration of the implant is its surface properties. The aim of this study was to investigate the bone response to dental implants with different surface characteristics using the rabbit tibia model. Tricalcium phosphate (TCP) coated, anodic oxidized and turned (control) surfaces were compared. MATERIALS AND METHODS: Seventy two implants were placed in the tibia of eighteen rabbits. Nine rabbits were sacrificed at 3 weeks of healing and the remaining nine were sacrificed at 6 weeks of healing. The bone-to-implant contact (BIC) and the bone volume density (BVD) were assessed by light microscope after 3 and 6 weeks of healing. RESULTS: Statistical analysis showed that no significant differences in the BIC and BVD were observed between the different implant surfaces and the control group at 3 weeks and 6 weeks of healing. Data also suggested that the BVD of all the surfaces showed significant difference at 3 and 6 weeks. CONCLUSION: The present study has showed that osseointegration occurred in all investigated types of surface-treated implants. In the current study all of the threads of the implants were observed to calculate BIC and BVD values (instead of choosing some of the threads from the bone cortex for example), which didn't make BIC or BVD percentage values better than in the control group, therefore the clinical relevance of these results remains to be shown.

Biomechanical evaluation of dental implants with different surfaces: Removal torque and resonance frequency analysis in rabbits

STATEMENT OF PROBLEM: Macroscopic and especially microscopic properties of implant surfaces play a major role in the osseous healing of dental implants. Dental implants with modified surfaces have shown stronger osseointegration than implants which are only turned (machined). Advanced surface modification techniques such as anodic oxidation and Ca-P application have been developed to achieve faster and stronger bonding between the host bone and the implant. PURPOSE: The purpose of this study was to investigate the effect of surface treatment of titanium dental implant on implant stability after insertion using the rabbit tibia model. MATERIAL AND METHODS: Three test groups were prepared: sandblasted, large-grit and acid-etched (SLA) implants, anodic oxidized implants, and anodized implants with Ca-P immersion. The turned implants served as control. Twenty rabbits received 80 implants in the tibia. Resonance frequencies were measured at the time of implant insertion, 2 weeks and 4 weeks of healing. Removal torque values (RTV) were measured 2 and 4 weeks after insertion. RESULTS: The implant stability quotient (ISQ) values of implants for resonance frequency analysis (RFA) increased significantly (P .05). The test and control implants also showed significantly higher ISQ values during 4 weeks of healing period (P .05). The SLA, anodized and Ca-P immersed implants showed higher RTVs at 2 and 4 weeks of healing than the machined one (P < .05). However, there was no significant difference among the experimental groups. CONCLUSION: The surface-modified implants appear to provide superior implant stability to the turned one. Under the limitation of this study, however, we suggest that neither anodic oxidation nor Ca-P immersion techniques have any advantage over the conventional SLA technique with respect to implant stability.

Histomorphometric Study of Dental Implants With RBM And SLA Surface In The Rabbit Tibia

The purpose of the present study was to evaluate the effects of several implant surface treatments to the bone formation, by placing Machined implants, 75 micrometer Calcium phosphate-blasted implants and Al2O3- blasted and acid-etched implants in rabbit tibia through histomorphometric study. Two animals of each group were sacrificed at 2, 4, 8 weeks. The specimens containing the implants were dehydrated and embedded into hard methylmethacrylate plastic. Thereafter, the sections were ground to 50 micrometer. The specimens were stained with Villanueva bone stain for a light microscopic study. The results were as follows; 1. When the surface roughness of three different implants was measured by Surfcorder, the Ra of the Machined group, the RBM group and the SLA group was 0.16 micrometer, 0.44 micrometer, and 1.08micro meter. 2. When examining the surfaces of the implants in the scanning microscope, Machined implant has the smooth surface with a few scratches, RBM implant has the rough surface with curled ridges and valleys, and SLA implant has the rough surface structures such as sharp protruding parts and micropits measuring 1-2 micrometer in diameter. 3. After 2 weeks of implantation, the percentage of bone-to-implant contact of the Machined group, the RBM group and the SLA group was 26.86%, 35.40% and 45.99%. However, its differences between each group decreased during the healing periods. 4. After 2 weeks of implantation, the percentage of bone area inside the threads of the Machined group, the RBM group and the SLA group were 21.55%, 30.43% and 41.18%. However, its difference of bone area between machined group and surface treatment groups was maintained but the difference within the surface treatment groups decreased during the healing periods. In summary, the amount of bone formation in RBM and SLA group was greater than Machined group in early healing stage. These results suggest that RBM and SLA implants can reduce the healing period for osseointegration and may be suitable for early function.

A study on the bone formation of graft material containing demineralized bone matrix with a simultaneous installation of implant

PURPOSE: The aim of the present study is to evaluate the effect of autogenous bone and allograft material coverd with a bioresorbable membrane on bone regeneration after a simultaneous installation of implant. MATERIALS AND METHODS: Twelve healthy rabbits, weighing about 3~4 kg, were used in this experiment. Following impalnt(with 3.25 mm diameter and 8 mm length) site preparation by surgical protocol of Oraltronics(R), artificial bony defect, 5mm sized in height and depth, was created on femoral condyle using trephine drill(with 5 mm diameter and 5 mm length). Then implant was inserted. In the experimental group A, the bony defect was filled with autogenous particulated bone and coverd with Lyoplant(R) resorbable membrane. In the experimental group B, the bony defect was filled with allograft material(Orthoblast II(R)) containing demineralized bone matrix and covered with Lyoplant(R). In the control group, without any graft materials, the bony defect was covered with Lyoplant(R). The experimental group A and B were divided into each 9 cases and control group into 3 cases. The experimental animals were sacrificed at 3, 6 and 8 weeks after surgery and block specimens were obtained. With histologic and histomorphometric analysis, we observed the histologic changes of the cells and bone formation after H-E staining and then, measured BIC and bone density with KAPPA Image Base(R) system. RESULTS: As a result of this experiment, bone formation and active remodeling process were examined in all experimental groups and the control. But, the ability of bone formation of the experimental group A was somewhat better than any other groups. Especially bone to-implant contact fraction ranged from 12.7% to 43.45% in the autogenous bone group and from 9.02% to 29.83% in DBM group, at 3 and 8 weeks. But, bone density ranged from 15.67% to 23.17% in the autogenous bone group and from 25.95% to 46.06% in DBM group at 3 and 6 weeks, respectively. Although the bone density of DBM group was better than that of autogenous bone group at 3 and 6weeks, the latter was better than the former at 8 weeks, 54.3% and 45.1%, respectively. Therefore these results showed that DBM enhanced the density of newly formed bone at least initially.

Clinical, histologic, and histometric evaluation of implants with microthreaded crest module and SLA surface / 대한치주과학회지

BACKGROUND: Crestal bone loss known as saucerization is a frequently observed phenomenon. Recent studies have shown that implants with micothreaded crest module reduced the force concentration in the crestal region thus resulting in no or reduced crestal bone loss. This study presents a clinical, histologic, and histometric evaluation of implants with microthreaded crest module and SLA surface. METHODS: The implants were placed in the mandible of 5 beagle dogs weighing 10-15kg. Four premolars were bilaterally extracted 8 weeks prior to implant placement. Mucoperiosteal flap was elevated and drilling with increasing diameter was performed under saline irrigation. After countersinking 2 implants were placed in each side resulting in 4 implants per dog. Healing period of 8 weeks was allowed before sacrificing the animals. Histologic preparation was performed for histologic and histometric analysis. Bone to implant contact as well as percentage of bone area inside threads were measured. T-test was used for statistical analysis with pvalue p<0.05. RESULTS: 1. Healing was uneventful without any cover screw exposure. New bone formation around the implants was observed without any inflammatory infiltration. 2. Bone to implant contact in the microthread and thread were 43.90 +/- 20.30 %, and 53.19 +/- 20.97 % respectively. The overall bone to implant contact was 48.54 +/- 20.95 %. 3. Percentage of bone area inside threads were 54.43 +/- 10.39 %, and 38.44 +/- 16.44 % for the microthread and thread respectively. There was statistically significant difference(p<0.05). The overall percentage of bone area inside threads was 46.67 +/- 15.68 %.

Removal Torque and Histometric Evaluations of Implants with Various Area of Hydroxyapatite Coating Placed in the Rabbit Tibia / 대한치주과학회지

BACKGROUND: This study presents a biomechanical and histometric comparison of bone response to implants with various area of hydroxyapatite(HA) coating. METHODS: The implants were placed in the tibia of 10 rabbits weighing 2.5-3.5kg. The control group had a machined surface, the experimental group 1 had 50micrometer thick HA coated in a band form, and the experimental group 2 had 50micrometer thick HA coated on the entire surface. 8 weeks after implantation, the animals were sacrificed. Removal torque was measured and histologic preparation was also performed for histologic and histometric analysis. Bone to implant contact as well as percentage of bone area inside threads were measured. ANOVA post hoc, and t-test were used for statistical analysis with p-value p<0.05. RESULTS: 1. The removal torques were 9.36 +/- 5.64 Ncm, 48.40 +/- 16.66 Ncm, and 82.37 +/- 22.56 Ncm for the control, exp. 1, and exp. 2 group respectively. Statistically significant difference were found among all the groups(p<0.05). 2. Bone to implant contact in the cortical bone were 38.94 +/- 10.9 %, 66.90 +/- 14.1 %, 73.00 +/- 19.4 %, in the marrow bone, 8.30 +/- 5.4 %, 14.59 +/- 5.9 %, 18.54 +/- 11.8 %, and in total, 22.40 +/- 10.1 %, 31.19 +/- 7.5 %, 41.41 +/- 12.2 % for the control, exp.1, and exp. 2 group respectively . In the cortical bone, exp. 1, and exp. 2 group showed statistically significantly higher contact compared to control group. Total contact and in the marrow bone, only exp. 2 group showed statistically significantly higher contact compared to control group(p<0.05). In all the groups significantly higher contact were observed in the cortical bone compared to the marrow bone(p<0.05). 3. Percentage of bone area inside threads in the cortical bone were 55.68 +/- 7.25 %, 55.19 +/- 13.19 %, 57.04 +/- 13.33 %, in the marrow bone, 12.34 +/- 14.61 %, 17.56 +/- 20.04 %, 20.26 +/- 12.83 %, and in total, 30.30 +/- 12.46 %, 31.57 +/- 15.15 %, 34.25 +/- 12.56 % for the control, exp.1, and exp. 2 group respectively. There was no statistical difference among the groups. In all the groups significantly higher bone area were observed in the cortical bone compared to the marrow bone(p<0.05)

Bone-to-Implant Contact according to the Surface Roughness of the Implants / 대한치주과학회지

This study was performed to evaluate the difference of the bone-to-implant contact according to the surface roughness of the implants. Two beagles were used in the experiment. Extraction of the all premolars was performed in the mandible. In 3 months of healing, screw-shaped pure titanium machined surface implants (Implantium(R), Dentium Co. Korea), implants blasted with 45micrometer TiO2 particles, (Implantium(R), Dentium Co. Korea) and implants blasted with 100micrometer TiO2 particles, (Implantium(R), Dentium Co. Korea) in diameter 3.4mm and length 6mm were installed in the edentulous mandible. Each dog was sacrificed at 4, 12 weeks after placement and then nondecalcified specimens were prepared for histologic analysis. The results of this study were as follows. 1. At 4, 12 weeks after the surgery, bone-to-implant contact in the surface blasted with TiO2 particles was higher than that in the pure titanium machined surface respectively. 2. Osseointegration in the surface blasted with 45micrometer TiO2 particles was more increased than that in the surface blasted with 100micrometer TiO2 particles. 3. Bone-to-implant contact was increased with time independent of surface roughness. 4. Bone formation was in the outfolded area more than inside the threads independent of surface roughness. From the above results, we were able to find the most bone-to-implant contact in 45micrometer TiO2 blasted implant.